Charged particle assessment tool, inspection method

Abstract

A multi-beam electron-optical system for a charged-particle assessment tool, the system comprising: a plurality of control lenses, a plurality of objective lenses and a controller. The plurality of control lenses are configured to control a parameter of a respective sub-beam. The plurality of objective lenses are configured to project one of the plurality of charged-particle beams onto a sample. The controller controls the control lenses and the objective lenses so that the charged particles are incident on the sample with a desired landing energy, demagnification and/or beam opening angle.

1 .- 20 . (canceled) 
     
     
         21 . A multi-beam charged-particle optical system for a charged-particle assessment tool, the system comprising:
 an objective lens array assembly comprising a plurality of aperture arrays, the objective lens array assembly configured to:
 focus a plurality of sub-beams on a sample; and 
 control a parameter of the sub-beams, the parameter being at least one of: landing energy of the sub-beams on the sample surface, opening angle of respective sub-beams, or magnification of respective sub-beams. 
   
     
     
         22 . The system of  claim 21 , wherein aperture arrays proximate to a sample are configured to focus the plurality of beams on the sample. 
     
     
         23 . The system of  claim 22 , wherein at least two aperture arrays are proximate the sample. 
     
     
         24 . The system of  claim 21 , wherein aperture arrays that are configured to control the parameter of the sub-beams are up beam of aperture arrays configured to control the focus of the sub-beams. 
     
     
         25 . The system of  claim 24 , wherein at least two aperture arrays are configured to control the parameter. 
     
     
         26 . The system of  claim 25 , wherein the aperture arrays configured to control the parameter comprise an aperture configured to control landing energy. 
     
     
         27 . The system of  claim 25 , wherein the aperture array configured to control the parameter comprise an aperture array configured to optimize the opening angle of respective sub-beams, or magnification of respective sub-beams. 
     
     
         28 . The system of  claim 27 , wherein the aperture array is the same as the aperture array configured to control landing energy. 
     
     
         29 . The system of  claim 21 , further comprising:
 a detector configured to detect charged particles emitted from the sample.   
     
     
         30 . The system of  claim 29 , wherein the detector comprises a plurality of detector elements, the plurality of detector elements being associated with respective sub-beams. 
     
     
         31 . The system of  claim 29 , wherein the detector is associated with the objective lens array assembly. 
     
     
         32 . The system of  claim 21 , wherein objective lens array assembly is electrostatic. 
     
     
         33 . The system of  claim 21 , wherein the charged particles are electrons. 
     
     
         34 . A charged-particle assessment tool, comprising:
 a multi-beam charged-particle optical system according to  claim 21 ; and   a condenser lens, the condenser lens being up beam of the objective lens array assembly and control lens array.